1. Field of the Invention
The present invention relates to the field of computers. More particularly, this invention relates to a battery switching circuit enabling simultaneous charging, sequential charging and sequential discharging of multiple batteries and a method for charging the batteries independent of their technology.
2. Art Related to the Present Invention
Over the last few years, portable computers have become one of the fastest growing computer-related products due to its versatility. For example, a portable computer may be used as a personal desktop computer when alternating current ("AC") power is available. In addition, portable computers may be used in "mobile" locations without AC power such as within a vehicle of transport, a job-site outside one's office and a variety of other locations. During use in such location, portable computers generally relay on their removable battery pack(s) for power.
A removable battery pack(s) having sufficient power storage capabilities is essential for portable computers since a portable computer must be able to continuously operate for a reasonable amount of time. Typically, a portable computer is designed with one removable battery pack since it is less costly to manufacture i.e., it requires less contacts, battery pack enclosures, and other components than portable computers having multiple battery packs. However, portable computers having a single battery pack are less expandable and less configurable than portable computers with multiple battery packs since the single battery pack always needs to be present in "mobile" locations and a second battery pack may be used for adding more battery capacity (hence, more run time) or for expanding functionality of the portable computer with a system bus expansion connector at this location. In addition, the user is usually incapable of accurately predicting how much battery run-time remains in the battery, lessening his or her sense of security when using the portable computer as a mobile unit.
Although conventional portable computers having duel removable battery packs are commercially available, these portable computers do not truly offer independent control of discharging and charging of the batteries, limiting benefits and flexibility in using such portable computers. Instead, they normally provide a rudimentary power distribution system, normally without software control, to minimally control the discharging as well as the charging of the batteries. The manner of discharge is usually simultaneous discharging of the batteries. As a result, the cost in designing and constructing the power distribution system is nominal. Although this feature may initially afford its consumers cost savings, there exists many disadvantages which greatly overshadow such savings.
One notable disadvantage is that consumers of portable computers having simultaneous discharging batteries are usually less capable of predicting when to change the batteries or when to charge them. As a result, the consumer may unknowingly over-discharge and possible degrade the batteries or refrain from charging the batteries when needed.
Another notable disadvantage is that the conventional portable computers are not able to reliably charge one battery while still operating at a maximum rate. Rather, the conventional portable computers need to operate in a mode having a slow operational speed or discontinue operations altogether to charge the batteries. Yet another disadvantage prevalent in the conventional power distribution system is that both batteries are almost never fully discharged since the portable computer will often drop into a low power of shutdown mode to avoid losing data or deeply discharging which damages the batteries. By not allowing full discharge of batteries, the batteries are more likely to develop "memory effects," where the batteries appear to lose capacity.
In addition, the conventional portable computers usually require its consumer to download additional software or modify hardware in the event that another battery technology, different from an originally intended technology, is used by the portable computer. For example, most battery packs used by conventional portable comprises Nickel Cadmium ("NiCad") and Nickel Metal Hydride ("NiMH") batteries (hereinafter collectively referred to as "Nickel batteries") which require a constant current regime for charging and follow a well-known negative change in voltage technique (NiCad) or well-known temperature gradient technique (NiMH) to ascertain when to terminate its charging. In the event that the consumer substitutes the Nickel batteries for a Lithium-Ion ("Li-Ion") battery, requiring a constant voltage regime and utilizing a well-known voltage detection and charging time-out technique to ascertain when to terminate its charging, it is likely that the consumer would have to at least upgrade its software and/or hardware to properly charge the Li-Ion battery. The present invention, however, provides an ability to charge or discharge any battery technology through a single battery charging algorithm without any modifications by the consumer.